1. Field of the Invention
The invention relates to a device and methods for ensuring proper curvature for a catheter placed in a patient and more particularly to an implantable catheter having a curved elastic brace.
2. Description of the Related Art
There are a number of conditions in patients for which it is desirable to add or withdraw fluid. Some fluid management conditions involve the mammalian brain. Within the cranium, gray and white matter is suspended in cerebrospinal fluid and nourished by blood delivered through cerebral arteries. The gray matter has closely spaced cell bodies of neurons, such as in the cerebral cortex, and the underlying white matter contains densely packed axons that transmit signals to other neurons. Human brain tissue has different densities and comprises approximately eighty percent of the intracranial content, with blood and cerebrospinal fluid each normally comprising approximately ten percent.
Cerebrospinal fluid is produced by choroid plexus in several connected chambers known as ventricles and typically is renewed four to five times per day. Cerebrospinal fluid in a healthy human flows slowly and continuously through the ventricles, propelled by pulsations of the cerebral arteries. The fluid flows around the brain tissues and the spinal column, and then through small openings into the arachnoid membrane, which is the middle layer of the meninges surrounding the brain parenchyma and ventricles, where the fluid is finally reabsorbed into the bloodstream.
Under normal conditions, bodily mechanisms compensate for a change in fluid volume within the cranium through tissue resilience and by adjusting the total volume of blood and cerebrospinal fluid so that a small increase in fluid volume does not increase intracranial pressure. Similarly, a healthy brain compensates for an increase in intracranial pressure to minimize a corresponding increase in intracranial volume. This volume- and pressure-relationship can be explained in terms of cerebral compliance, which term is intended to include herein the terms elastance and intracranial compliance.
The brain is compliant as long as a person's auto-regulatory mechanism can compensate for any change in volume. As soon as the brain's auto-regulation or compensatory mechanisms fail, blood and cerebrospinal fluid cannot be displaced, and the brain can no longer adapt to any increase in fluid volume. A reduction in cerebral compliance eventually will lead to an undesired increase in intracranial pressure, also known as hydrocephalus. As more fluid volume is added, a threshold is reached beyond which small increases in volume lead to dramatic and unhealthy increases in intracranial pressure.
A typical device to treat fluid conditions such as hydrocephalus is a ventricular catheter disclosed by Watson et al. in U.S. Pat. No. 5,738,666. In one embodiment, ventricular catheter 22 has a plurality of fluid management openings, referred to as fluid flow apertures 56, near a distal tip 58 having a slit 60. The “distal” tip is the end farthest from a surgeon during implantation of the catheter. A terminal end 40 of a rigid introducer cannula 34 is inserted through the slit 60 during final placement of the ventricular catheter. A Tuohy-Borst adaptor 32 is secured to the proximal end of the introducer cannula 34. During set-up, a fiber-optic shaft 66 of an endoscope is advanced through the adaptor 32 and the cannula 34 until a fiber-optic terminal end 28 emerges past ventricular catheter terminal end 58 and aligns with introducer terminal end 40. Fiber-optic shaft 66 is then interlocked relative to introducer cannula 34. The aligned tips of the fiber-optic shaft 66 and the introducer cannula are then retracted proximally within catheter 22 during advancement through tissue until a selected ventricle is reached.
Unfortunately, complications associated with the ingrowth of choroid plexus into implanted ventricular catheters, also known as ventricular shunts, are common. The most common cause of ventricular shunt malfunction during treatment of hydrocephalus is occlusion, sometimes referred to as proximal shunt occlusion, with the fluid management openings frequently blocked by choroid plexus and/or brain parenchyma. Accurate placement of the catheter depends on both proper insertion trajectory and proper catheter tip positioning vis-a-vis ventricular configuration. Surgeons often attempt to place the distal tip of the ventricular catheter in front of the foramen of Monro to avoid the choroid plexus. However, creating a direct path to the front region restricts the surgical approaches to the ventricle. Theories on how the approaches differ based on seizure risk, choroid plexus obstruction, size and shape of target ventricular chamber and incidence of infection remain controversial.
Pre-curved catheters have been utilized for a variety of applications, typically where larger outer diameters are tolerated. U.S. Pat. No. 3,867,945 by Wendell Long discloses a Foley urethral catheter with a stylet that is semi-rigid and sufficiently stiff with an optimal curvature to guide the catheter during insertion.
Reinforced retention structures having an elastic member are disclosed by Teague et al. in U.S. Pat. No. 6,569,150. The retention structure provides an anchoring geometry to retain a catheter in position within the body of a patient, such as within a kidney and ureter.
It is therefore desirable to have a more versatile device and technique for positioning a catheter to manage bodily fluids, especially cerebrospinal fluid. A device is needed that minimizes obstruction and failure of a shunt system by facilitating the final catheter position within a ventricle of a brain, particularly when a more challenging occipital approach is utilized.